Handicapping Facebook and Abercrombie

Can the social-network stock dispel a few nagging concerns? And is Abercrombie as good a buy as its merchandise?

Anyone looking to sketch a design for a thrilling amusement-park roller coaster might want to start with the stock chart of Facebook.

Upon hitting $45 a share on its first day of trading last May, Facebook (ticker: FB) quickly began to disappoint its many supporters, falling to an intraday low of $17.55 in mid-November. Then, as the bears...